Electronic devices include traditional computing devices such as desktop computers, notebook computers, smartphones, wearable devices like a smartwatch, internet servers, and the like. However, electronic devices also include other types of computing devices such as personal voice assistants, thermostats, automotive electronics, robotics, devices embedded in other machines like refrigerators and industrial tools, Internet-of-Things (IoTs) devices, and so forth. These various electronic devices provide information, entertainment, social interaction, security, safety, productivity, transportation, and other services to human users. Thus, electronic devices play crucial roles in many aspects of modern society.
Many of the services provided by electronic devices in today's interconnected world depend at least partly on electronic communications. Electronic communications can include those exchanged between or among distributed electronic devices using wireless or wired signals that are transmitted over one or more networks, such as the Internet or a cellular network. Electronic communications can also include those exchanged between or among different printed circuit boards, modules, chips, or cores of a given integrated circuit within a single electronic device. Regardless, electronic communications are usually accomplished by generating or propagating signals. Typically, such electronic communications are performed using at least one signal that is designed to have a specified frequency. Generally, communication signals are more likely to be correctly transmitted and received, as well as accurately interpreted, if the specified frequency is accurately created and reliably maintained.
A phase-locked loop (PLL) is often used to create, or synthesize, a desired frequency. In fact, a phase-locked loop is typically a core part of a frequency synthesizer, which is a component that is employed by electronic devices to synthesize signals having different frequencies. In operation, a phase-locked loop receives a reference signal and applies the reference signal to a feedback loop. Using the feedback loop, the circuitry of the phase-locked loop generates an output signal that oscillates at a desired frequency in a stable and accurate manner. Typically, the phase-locked loop derives the frequency of the oscillating output signal from the reference signal, such as by being some multiple of the reference signal.
A PLL-based frequency synthesizer thus outputs an oscillating signal having some desired frequency. The electronic device then uses the synthesized frequency of the output signal in one or more stages of a communication scenario. Example stages for communicating an electromagnetic signal include generating, transmitting, receiving, or interpreting a communication signal. For an example signal generation stage, a frequency generated by a phase-locked loop can be used to modulate a communication signal. Here, the modulation entails adding information—such as a text and an associated photograph—to the communication signal. For an example signal transmission stage, the frequency generated by a phase-locked loop can be employed to upconvert a frequency of a communication signal using a mixer. With an up-conversion operation, the mixer increases the frequency of the communication signal, such as to enable the communication signal to be transmitted wirelessly as a radio frequency (RF) signal. A phase-locked loop can also be used on the receiving side of a typical communication scenario. For instance, a phase-locked loop can be used to down-convert a frequency of a received communication signal or to demodulate the received communication signal to recover the encoded information, such as the text message with the associated photograph.
Thus, phase-locked loops are employed in multiple stages of a communication scenario to support electronic communications with electronic devices. Consequently, electrical engineers and other designers of electronic devices strive to improve the functionality and usability of phase-locked loops to facilitate electronic communications with electronic devices.